The controversy over a police surveillance network embedded in the environmental protest movement has deepened dramatically after the Guardian identified a second undercover officer who spent years living a double life as an activist.

Senior police chiefs said they were concerned for the safety of the second spy, and a major operation involving several UK forces is now under way to identify other operatives whose safety may have been compromised by Kennedy.

The second spy spent four years living as an environmental activist in Leeds, gaining the trust of dozens of activists and playing a central role in planning a demonstration to shut down Drax power station in North Yorkshire.

Her deployment ended in 2008, when she told activist friends she was leaving town for personal reasons. The Guardian has established the identity of the officer, who is from a force in the south-east of England, but has decided, after representations from senior police officers, to refer to her only as Officer A, and to use pixellated pictures of her.

Meanwhile politicians across Europe demanded information about the activities of Kennedy, the first undercover operative identified, who was on Tuesday accused of having had several sexual relationships with activists while undercover. Senior police sources have described these relationships as "unacceptable".

His UK-based handlers have flown to the US in an attempt to find an agent now accepted to have "gone rogue".

Aside from questions over his conduct while undercover, Kennedy, a Metropolitan police officer, committed a serious breach of protocol when he told friends from the protest movement that Officer A was his colleague. A police chief with detailed knowledge of the deployments of undercover officers in the protest movement said Kennedy's breach of protocol could lead to the "relocation of a considerable number of people".

That included undercover officers currently involved in ongoing police investigations across the UK and their families. "This is serious stuff," the police chief said. "Lots of people are at risk – their lives are at risk."

Kennedy, who has expressed remorse over an operation he told friends was "wrong", now appears to have been a key player in a pan-European network of leftwing and environmental groups.

Using a fake passport, he travelled to more than 22 countries from his base in Nottingham. A parliamentarian in Germany said Kennedy had been "operating on the border of illegality" in the country, and demanded disclosure about the operation. Kennedy's activities in Iceland, Ireland and Italy are also coming under scrutiny.

Documents obtained by the Guardian also suggest that, after quitting the Met last March, Kennedy attempted to continue to use his adopted identity to infiltrate protest groups. In an indication he planned to turn his hand to corporate espionage, Kennedy, who is said to have had money problems, set up two companies. One is connected to an individual who previously worked at Global Open, a private security firm set up by a former special branch detective. The company specialises in keeping a "discreet watch" on protest groups.

Police chiefs discussed the unfolding crisis at a meeting of the Association of Chief Police Officers (Acpo) yesterday, which has limited company status and to which Kennedy and Officer A were seconded.

It is now believed several undercover police officers have been living long-term in the environmental movement, feeding intelligence back to the National Public Order Intelligence Unit (NPOIU), an Acpo body that runs a nationwide intelligence database of political activists. After concerns were raised about the accountability of NPOIU, police chiefs came up with a plan to move the unit to Scotland Yard. Subject to agreement, the unit will be taken over by Met officers next month.

However, a major review will now be under way into the oversight of officers such as Kennedy. Explaining why he and Officer A had spent so long undercover, the police chief said: "It is simply because of the environment. If you are a deeply ideologically motivated person … then getting close to you to understand your thought processes – and some idea of what you're doing – takes a lot longer."

He added that Kennedy's numerous sexual relations with women would not have been officially sanctioned. "That is conduct that is not acceptable," he said.